Method and apparatus for grinding drills



June 5, 1962 H. ERNST ETAL 3,037,329

METHOD AND APPARATUS FOR GRINDING DRILLS Filed Sept. 20, 1957 11Sheets-Sheet 1 INVENTO RS HANS ERNST WILLIAM A.HAGGERTY EUGENE L. RITTERATTORNEYS June 5, 1962 H. ERNST ETAL 3,037,329

METHOD AND APPARATUS FOR GRINDING DRILLS Filed Sept. 20, 1957 11Sheets-Sheet 2 ATTORNEYS June 5, 1962 H. ERNST ETAL METHOD AND APPARATUSFOR GRINDING DRILLS l1 Sheets-Sheet 3 INVENTORS HANS ERNST WILLIAM A.HAG

Filed Sept. 20, 1957 GERTY EUGENE L. RITTER BY r/YT/Cu'Q-M- ATTORNEYSJune 5, 1962 H. ERNST ETAL 3,

METHOD AND APPARATUS FOR GRINDING DRILLS Filed Sept. 20, 1957 llSheets-Sheet 4 lNVENTORS HANS ERNST WILLIAM A.HAGGERTY EUGENE L. RITTERATTORNEYS June 5, 1962 H. ERNST ETAL METHOD AND APPARATUS FOR GRINDINGDRILLS l1 Sheets-Sheet 5 Filed Sept. 20, 1957 Raw Ill m n INVENTORS HANSERNST WILLIAM A.HAGGERTY EUGENE L. RITTER ATTORNEYS June 5, 1962 H.ERNST ETAL 3,037,329

METHOD AND APPARATUS FOR GRINDING DRILLS Filed Sept. 20, 1957 llSheets-Sheet 6 A30 /2a /53 I52 /29 5a /5/ J /2/ ///a //7 //6' //.9 [/5I47 9 M4 g5 fl 141g. 9-

WILLIAM A. HAGGERTY EUGENE L. RITTER ATTORNEYS June 5, 1962 H. ERNSTETAL METHOD AND APPARATUS FOR GRINDING DRILLS Filed Sept. 20, 1957 llSheets-Sheet 7 WILLIAM A.HAGGERTY EUGEN E L.R|TTER ATTORNEYS June 5,1962 H. ERNST ETAL METHOD AND APPARATUS FOR GRINDING DRILLS Filed Sept.20, 1957 ll Sheets-Sheet 8 Q wmw Nu N m mmN INVENTORS HANS ERNST WILLIAMA.HAGGERTY EUGENE L.RlTTER riff/dam AT TO RNEYS June 5, 1962 H'. ERNSTETAL METHOD AND APPARATUS FOR GRINDING DRILLS l1 Sheets-Sheet 9 FiledSept. 20, 1957 INVENTORS HANS ERNST ILLIAM A. HAGGERTY EUGENE L. RITTERATTORNEYS June 5, 1962 H. ERNST ETAL 3,037,329

' METHOD AND APPARATUS FOR GRINDING DRILLS Filed Sept. 20, 1957 llSheets-Sheet 10 INVENTORS HANS ERNST [8 WILLIAM A.HAGGERTY EUGENEL.RITTER BY ,mzwwf wv ATTORNEYS June 5, 1962 H. ERNST ETAL 3,037,329

METHOD AND APPARATUS FOR GRINDING DRILLS Filed Sept. 20, 1957 llSheetsSheet 11 4 m z; m T(?; N

INVENTORS HANS ERNST N Q q) WILLIAM A.HAGGERTY EUGENE L.R|TTER ATTORNEYS atenr- 3,037,329 Patented June 5, 1962 thee 3,037,329 METHOD ANDAPPARATUS FUR GRINDING DRILLS;

Hans Ernst, William A. Haggerty, and Eugene L. Ritter, all ofCincinnati, Ohio, assignors to The Eincinnati Milling Machine Co.,Cincinnati, Ohio, a corporation of Ohio Filed Sept. 20, 1957, Ser. No.685,212 22 Claims. (Cl. 51-43) This invention relates to a new andimproved method and apparatus for grinding metal Working drills.

The method and apparatus of this invention is directed more particularlyto the manufacture of the improved type of drill shown in co-pendingapplication Serial No. 566,504, filed February 20, 1956, in the UnitedStates Patent Office, now Ptaent No. 2,903,922, dated September 15,1959.

It is desirable in metal working drills that the tip end of the drillshould act as a pilot means for centering the drill at the spot wherethe hole is to be drilled, but conventional drills are unsatisfactory inthis respect in that they have chisel edge at the tip which isineffective for centering and pilot purposes because it is a straightline edge perpendicular to the axis of the drill. A more satisfactorydrill would be one having some form of selfcentering pilot means at thetip of the drill, but it also must be such that it can be generated aspart of the grinding process of sharpening the main cutting edges on thedrill and thus not require a separate operation.

Shapes might be conceived or designed for the end of a drill which couldnot be generated in a single generative grinding cycle, and since it ispreferable to utilize a grinding wheel for the sharpening process, theproblem of generation with a revolving body such as a rotatable grindingwheel becomes involved and sets up design limitations.

This invention, therefore, deals with a new and improved process andapparatus for not only generating the new and improved form of pilotmeans on the drill shown in the co-pending application, but. a methodand apparatus which is so contrived that the entire end of the drillincluding the pilot means and cutting edges may be ground in acontinuous generative grinding operation automatically, the arrangementbeing such that the generative cycle repeats automatically for each maincutting edge to be ground or sharpened.

One of the objects of this invention is to provide a new and improvedmethod of generatively grinding the end of a metal working drill toproduce a drill having improved centering and cutting characteristics.

Another object of this invention is to provide a new and improvedapparatus for performing the method of this invention.

A further object of this invention is to provide a new and improvedmethod of the character described which will produce a new and improvedtip on a drill and one which can be generated in the same cycle with thegeneration or grinding of the main cutting edges on the end of thedrill.

Another object of this inventionis to provide a new and improved methodof the character described in which a rotatable grinding Wheel may beutilized as the generating agent.

Other objects and advantages of the present invention should be readilyapparent by reference to the following specification, considered inconjunction with the accompanying drawings forming a part thereof, andit is to be understood that any modifications may be made in the exactstructural details there shown and described. with- 2 in the scope ofthe appended claims, without departing from or exceeding the spirit ofthe invention.

Referring to the drawings in which like reference numerals indicate likeor similar parts:

FIGURE 1 is a view in elevation of a machine em-. bodying the principlesof this invention.

FIGURE 2 is a plan section on the line 2-2- of FIG- URE 1.

FIGURE 3 is a section on the line 3-3 of FIGURE 1.

FIGURE 4 is a vertical section on the line 4-4 of FIGURE 1 showing thelever mechanism for shifting the tool carriage laterally.

FIGURE 5 is a detail section on the line 5-5' of FIG- URE 12.

FIGURE 6 is a section on the line 66 of FIG- URE 4.

FIGURE 7 is a View on the line 77 of FIGURE 6.

FIGURE 8 is a plan view on the line 88 of FIG- URE 1.

FIGURE 9 is a sectional view on the line 9-9 of FIGURE 8.

FIGURE 10 is a section through the work holder taken on the line 1i10 ofFIGURE 1.

FIGURE 11 is a plan view of the work holder on the line 11-11 of FIGURE10.

FIGURE 12 is a detail section taken on the line 1212 of FIGURE 1.

FIGURE 13 is a detail section on the line 1313 of FIGURE 11.

FIGURE 14 is a detail section on the line 14-14 of FIGURE 13.

FIGURE 15 is a view of one of the lateral control cams of the machine asviewed on the line 1515 of FIGURE 1.

FIGURE 16 is a section on the line 1616 of FIG- URE 15.

FIGURE 17 is a diagram of the position of the grinding wheel in itscycle of movement related to a fixed position of the drill.

FIGURES 18, 19, and 20 show difierent instantaneous positions of thegrinding wheel as it moves through its cycle about the drill.

FIGURES 21, 22, and 23 show diiferent arrangements of the drill withrespect to a grinding element.

The method and machine of this invention is designed for manufacturingthe ends of drills, such as metal working drills, to provide a new andimproved cutting face thereon, and may be utilized either initially toform a cutting face on the end of drill blanks, or for refinishing andresharpening the cutting edges thereon. This method and machine aredesigned more particularly for pointing drills of the type disclosed inU.S. Patent No. 2,903,922.

Since the entire end surface of a drill including the cutting edges orlips is that portion of the drill that does the cutting, the entire endsurface of the drill may be conveniently termed herein as the cuttingface of the drill.

In general, the method of this invention includes the steps ofpositioning the axis of a drill in a plane containing the axis of agrinding wheel, and at a suitable angle to the working face of thegrinding wheel or the like, and then effecting a three dimensionalrelative movement between said faces in a substantially conical spiralpath.

This can be accomplished in various ways. For instance, as shown inFIGURE 21, a conical shaped grinding wheel 25 may be utilized, and thedrill axis 26 maybe arranged in a radial plane of the wheel thatcontains its axis 27 and at an acute angle to the working face thereof:or the drill axis 26 may be arranged perpendicular to the axis 27 of thewheel 25 and at an acute angle to the working face thereof as shown inFIGURE 22. Again, the axis of the drill 2 6 may be positioned at anacute angle to the working face of a cylindrical grinding wheel 28 whilelying in a radial plane through its axis 27 as shown in FIGURE 23. Ineach case the axis of the drill lies in a radial plane containing theaxis of the grinding wheel and at an angle to the working or grindingface thereof, it being understood that this angle will vary inaccordance with the point angle of the drill.

The line of intersection of the radial plane with the periphery of thewheel is indicated as AB in these figures and constitutes one of thegenerative line elements in the surface of the wheel, and this lineelement terminates at a corner of the wheel which is provided preferablywith a small radius as shown at B. At this corner, the line elementmeets a reference axis GG at an angle. The reference axis is alwaysparallel to the drill axis.

Neglecting rotation of the grinding Wheel, it will be obvious that bysweeping the active line element such as AB over the surface of thedrill in a properly guided movement, a desired shape of surface can beproduced or generated. Of course, the same effect would be produced ifthe drill surface were moved instead of the line.

When it is selected that the grinding wheel do the sweeping, thereference axis GG is utilized as the axis of gyration of the grindingWheel, whereas when the drill does the moving about the wheel, the axisof the grinding wheel becomes the axis of gyration or rotation. If thegrinding wheel axis is fixed, and the drill rotated, the axis of thedrill becomes the axis of gyration. It will thus be seen that in thegenerating process either the grinding wheel axis or the drill axis maybe held stationary while the other is moved; or part of the movementsmay be applied to one and the remaining movement to the other. Hereinthe active line element of a rotating grinding wheel is considered to bethe one that is instantaneously tangent to the surface being ground.

Having properly positioned the parts in accordance with the first step,the three dimensional generative movement is performed by moving oneface bodily relative to the other such as relatively moving one of theparts toward the other, as indicated by the arrow F in these figures,and simultaneously effecting a second movement laterally of the firstmovement in the direction of the arrow L which produces a resultantmovement generally along and parallel to the active generative lineelement A-B. If the grinding wheel does the moving, then the directionof the arrows is reversed.

In addition to this compound movement, a circular or gyrating motion issimultaneously effected between wheel and drill in order to sweep thegeneratrix over the end surface of the drill and thereby effect a threedimensional grinding operation. The last-named motion is effected abouta gyratory axis by moving the wheel about the drill, the drill about thewheel, or simply rotating the drill itself about its own axis. Thecompound linear movement and the gyratory motion are effectedsimultaneously with the result that a conical spiral cutting path isgenerated, and this action is repeated for each lip to be ground on thedrill.

Thus, the method consists of positioning the axis of the drill in aradial plane of a grinding wheel, with the drill axis at a suitableangle to a line element in the surface of the wheel lying in said plane,effecting relative movement between the drill face and the grindingwheel face along normally related lines, one of which is the axis of thedrill, and simultaneously effecting a gyratory movement of one of themembers about a gyratory axis lying in said radial plane of the grindingwheel and parallel to the drill axis.

The generating cycle for grinding each lip must be started in properrelation to the lip to be ground in order 4 to grind part of the tipportion before grinding the lip portion.

This is done by theoretically positioning the active line element of thegrinding wheel substantially midway of the flute. At the same time, theactive line element AB overlies the center of the drill, as shown inFIGURE 18. Thus, as the active line element sweeps over the fluteportion toward the lip only the tip portion will be ground.

As the rotation continues and the lateral movement L continues, thegrinding wheel will clear the tip which is necessary so that thecontinued axial movement necessary to grind the lip will not grind offthe tip, but leave it upstanding. After a predetermined rotationsufficient to grind the lip portion the parts are separated andrepositioned for grinding the next lip.

Although the machine or apparatus for carrying out the principles ofthis invention will vary in accordance with the arrangement of theparts, some of which are shown in FIGURES 21, 22, and 23, the machinewill still conform to the method disclosed. It will, therefore, besimpler to explain this invention by selecting one of the arrangementsillustrating the method. To this end, the invention will be described,utilizing the arrangement shown in FIGURE 21 and imparting all themotions to the grinding wheel to produce a conical spiral orthree-dimensional spiral cutting path. For simplicity, it will also beexplained in connection with a two-lip twist drill, but it will beunderstood that the same principles will apply to drills having morethan two flutes, because the method or generating cycle is merelyrepeated for each lip to be ground.

In FIGURES 18, 19, and 20 are views showing the grinding of a twistdrill 29 in accordance with this invention. In these views, the axis ofthe drill and the grinding wheel are parallel in accordance with thearrangement shown in FIGURE 21. The axis of gyration of the grindingwheel is indicated at G--G. The machine construction is such that itprovides such an axis to which all the movements described herein areimparted, and so in these FIGURES 17, 18, 19 and 20, it can beconsidered that this axis moves relative to the drill for ease ofunderstanding. It will be obvious that the first contact of the drill bythe wheel will be the highest point axially on the cutting face of thedrill as shown in FIG- URE 18 because the Wheel then moves on andaxially into the drill as shown in FIGURES 19 and 20. Therefore, it isnecessary to select a starting line on the cutting face of the drillwhich represents the highest point to be ground, and to insure that thewheel is so positioned in its orbit about the drill that the wheel willfirst contact this line as it starts to grind. For the purposes of thisexplanation the drill is held stationary and clamped in a fixture in themachine. Thus, all motions are imparted to the grinding wheel and itsaxis of gyration. In FIGURE 17 are shown some of the positions of thegrinding wheel as it moves about the drill in its gyratory path, andFIGURES l8, l9, and 20 illustrate instantaneous positions of thegrinding wheel in this path.

Considering FIGURES 17 and 18 together, FIGURE 18 shows the grindingwheel just touching the drill and thus just starting to grind. In FIGURE17 the corresponding position of the grinding wheel 25 is indicated bythe position Mia- 18a. The line 30 represents the position of the activeline element AB on the grinding wheel, and it will be noted that itoverlies the midportion of the flute 40 of the drill. The grinding wheelthen moves clockwise in its orbit to the position 19a19a shown in FIGURE17, and simultaneously in an axial direction as indicated by the arrow31 in FIGURE 18 and laterally in the direction indicated by the arrow 32in FIGURE 18, which puts the grinding wheel in the position shown inFIGURE 19.

The wheel continues in its orbit to the position 20a- 20a in FIGURE 17while simultaneously continuing its,

axial and lateral movements in the same directions which puts the wheelin the position shown in FIGURE 20. This completes the grinding of thearea 33 between the cutting lip 34 and the arcuate rim 35 of the nextflute 36. The same cycle is repeated for grinding the area 37 betweenthe next cutting lip 38 and the arcuate rim 39 of the next flute 40.

However, before repeating the cycle to grind'the area 37, it isnecessary to retract the grinding wheel quickly and shift it laterallyand axially in a reverse direction as it continues in its orbitalmovement until it is in the same relative position with respect to thedrill as shown in FIGURE 18 but displaced 180 degrees therefrom. Thegrinding will now start on the line 41, shown in FIGURE 17. The grindingwheel is now in the position 18b- 1'8b and continues to position 19b19band finally finishes grinding when in the position 2tlb-2hb. A secondretractive movement is now quickly efiected as the grinding wheelcompletes its orbit back to the starting position I'Sa-lSa.

It will now be noted in FIGURE 17 that the center lines 26a and 26bcross at the center on axis 26 of the drill and that in reality thegyratory axis G travels back and forth along the center line 26a from G1to G2 even though perpendicular to it. Thus, while the axis G is movingaway from the center of the drill along the center line 26a, one lip isbeing automatically ground, it being remembered that an axial movementperpendicular to the drawing is also taking place simultaneously. At theend of grinding, the axis G is quickly repositioned to the other side ofthe drill center, and the next lip is ground. Thus, in one completecircle, each lip is ground in an automatic cycle, and the automaticcycle automatically repeats itself. Means are provided for independentlyfeeding the drill axially toward the grinding wheel to take off as muchstock as is necessary to properly grind and sharpen the drill.

A good embodiment of a machine for carrying out the process of thisinvention will now be described. Referring to FIGURE 2, a conical-shapedgrinding wheel 25, is suitably mounted in a chuck 50 which is secured tothe end of a spindle 51. The spindle is supported by anti-frictionbearings 52 in a carrier 53. The rear end of the spindle 51 is providedwith a drive pinion 54 which intermeshes with an internal gear 55. Thecarrier 53 is supported for rotation by suitable anti-friction bearings56 in a support 57. Attention is invited to the fact that the spindle 51is eccentrically mounted in the carrier 53 by an amount indicated by thedistance 53 in FIGURE 2, which is preferably equal to the radius of thegrinding wheel 25 and indicated by the reference numeral 59. It will nowbe seen that the periphery of the grinding wheel always passes throughthe axis 64 of rotation of the carrier 53, and this axis corresponds tothe reference axis G-G.

The carrier has integrally connected therewith a drive gear 60 whichmeshes with a drive pinion 61 mounted on the end of a shaft 62, theshaft being anti-frictionally journaled at 63 in the support 57. It willnow be apparent that if the support 57 was held stationary and thecarrier 53 rotated, it would move the grinding wheel 25 bodily in acircle about the axis of rotation 64 of the carrier, and throughout thisrotation the periphery of the grinding wheel 25 would always passthrough or be tangent to the axis 64.

As shown in FIGURE 2, the drill 29 is mounted in a fixture, indicatedgenerally by the reference numeral 65, so that the axis 26 of the drillis parallel to the axis of rotation 67- of the spindle 51 and grindingwheel 25. It will thus be seen that if the axis of rotation 64 of thecarrier 53 is aligned withthe axis 26 of the drill that rotation of thecarrier will move the grinding wheel 25 in an orbit about the axis ofthe drill, and in this case the orbit would be a circle.

Since all movements are to be imparted to the grinding wheel in thisconstruction, the grinding wheel must be capable of axial movements aswell as lateral movements, and therefore the support 57 is, in turn,mounted for two directional movement at right angles to each other.

As shown in FIGURE 4, the support 57 is provided with depending lugs orbosses, one of which is indicated by the reference numeral 63 located atone side of the axis of rotation 64 of the carrier, and two of which arelocated on the other side of the axis and indicated by the referencenumerals 69 and 70 as shown in FIG- URE 3. It will be noted that thebosses form a threepoint support for the member 57. The boss 68 has abore 71 through which passes a supporting rod or guide 72 that isanchored in a sub-support 73. Likewise, the bosses 69 and 70 havesuitably formed bores by which they are supported on a guide rod 74which is also anchored in the sub-support 73. It will be noted thatthere is sufiicient clearance between the bosses and the subsupport topermit longitudinal sliding movement of the member 57 and a spring 75 isinterposed between the boss 70 and acollar 76 which is pinned at 77 tothe rod 74. The spring 75 exerts a constant urge in a direction toaxially retract the grinding wheel 25 from the drill 29 as shown inFIGURE 2.

The sub-support 73 also has three bosses, 78, 79, and 80, in which areformed suitable bores so that the bosses 78 and 79 are slidably mountedon a guide rod 81, and the boss 80 is guided on a guide rod 82. Theguide rods 81 and 82 are suitably anchored in the bed 83 of the machine.A spring 84 is interposed between the boss 78 and a collar 85 suitablysecured as by a pin 86 to the guide rod 31 whereby the spring 84continuously urges the sub-support 73 and grinding wheel carried therebyaway from the axis of. the drill 29 in a horizontal plane as viewed inFIGURE 2. It will now be seen that the grinding wheel 25 is supportedfor three different movements, i.e., a planetary movement about thedrill 29 by virtue of the rotary carrier 53, an axial movement and alateral movement with respect to the drill 29 by virtue of thetwo-directional slidable support 57.

The power drive mechanism for rotating the carrier 53 and the grindingwheel '25 is shown in FIGURE 2 and comprises a motor 87 which issupported on the movable frame 57, and has a drive shaft 88 which iscoupled to a shaft 89 anti-trictionally mounted in the frame 57. Theshaft 89 carries a pinion 90 which meshes with a gear 91. The gear 91forms part of reduction gearing shown in FIGURE 4 in which it will beseen that the gear 91 is supported on a stub shaft 92 which also carriesa gear 93 integral with the gear 9 1 and in mesh with a large gear 94which is supported for free rotation on shaft 62 as shown in FIGURE 2.

The gear 94 is connected by clutch teeth 95 to a shiftable clutch member96 which is keyed at 97 to the shaft 62. A spring 98 is interposedbetween the clutch member 96 and a flange 99 secured to the shaft 62 formaintaining the clutch member in driving engagement with the gear 94.The clutch member 96 may be disengaged by a clutch shifter fork 100. Theshaft 89 also has directly secured thereto the internal gear 55, whichis the drive gear for the grinding wheel, whereby it will be seen thatthe motor 87 drives directly through the shaft '89 to the internal gear55 to effect high speed rotation of the grinding wheel, but drivesthrough the reduction gearing 91, 93, and 94 to the pinion 61 to effecta relatively slow rotation to the carrier 53.

The rear end ofthe carrier 53 has a cam member 101 secured thereto as byscrews 102, and it will be noted from FIGURE 3 that the spring 75 iseffective to urge the cam member 101 toward the right as viewed in FIG-URE 2 and that the spring 84 is effective to urge the cam member 101toward the bottom of the drawing as shown in FIGURE 2. The axialmovement of the carrier 53 is opposed by a cam roller 103 which rides inengagement with a cam surface 104 formed on the memher 101. The lateralmovement of the carrier 53 is opposed by a cam follower 105 which ridesin engagement with a peripheral earn surface 106 formed on the member101. Attention is invited to the fact that the cam rollers 103 and 105are held stationary during the operation of the machine, and, therefore,as viewed in FIGURE 2, any rise in the cam surface 104 will cause axialmovement of the grinding wheel 25 toward the drill 29 and that any risein the cam surface 106 will cause movement of the grinding wheel 25laterally of the axis of the drill. The cam roller 105 is rotatablysupported on the end of a lever arm 136 which is pivotally supported ona pin 107 located in the support 57 as shown in FIG- URE 4.

The lever arm 136 has a fulcrum surface 108 which engages with anadjustable fulcrum roller 109. The roller 109 is mounted in a bracket,indicated generally by the reference numeral 110, said bracket beingguided at 111 and 112 on a vertical guide rod 113 which is anchored inthe bed of the machine.

The bracket 110, as shown in FIGURE 1, has a lateral extension 114which, as shown in FIGURE 9, has a threaded hole 115 in which isthreaded a vertical adjusting screw 116. The screw 116 extends throughthe top of the fixed housing 117 of the machine and has a reducedportion 118 upon which is mounted a flange bushing 119. The bushing isheld in position by a circular plate 120 which is fastened to the top ofthe housing as by screws 121. The reduced portion 118 also has anaxially serrated portion 122 in the form of fine gear teeth upon whichis slidably mounted a pinion gear 123, which has an elongated hub thatabuts against the end of a rotator 124 which is also mounted on thereduced end 118. A cap screw 125 is threaded in the end of the screw 116and overlaps the rotator 124 to hold the parts in position on the screw116. The rotator 124 has a manually operable handle 126. When therotator 124 is moved by the handle 126, the gear 123 is rotated, andthrough idler gear 127 (FIG. 8), rotates the coupled gears 128 and 129mounted on a pin 130 which is fixed in the plate 120. The gear 129intermeshes with a large internal gear 131 formed on the inside of adial plate 132. It will be seen that the gearing arrangement forms areduction in the drive between the screw 116 and the plate 132 whereby alarge number of revolutions must be imparted to the screw in order toeffect one rotation of the dial 132. In fact, the reduction issuflicient that the screw 116 may be rotated the necessary number oftimes to move the fulcrum roller 109 through its complete range oftravel while only effecting one revolution of the dial plate 132. Thisadjusting mechanism is for the purpose of varying the throw effected bythe cam 106 in moving the grinding wheel laterally, and the lateralmovement is adjusted in accordance with the diameter of the drill beingground. Therefore, the setting for different diameters of drills may beindicated by placing the drill diameter sizes sequentially in the boxes133 on the side of the indicator plate 132 as shown in FIGURE 8.

As viewed in FIGURE 4, the action of the fulcrum mechanism will bebetter understood if it is remembered that the spring 84 shown in FIGURE3 is continuously acting on the slide 57 to push the pin 107 and the cam106 against opposite ends of the lever 136, and this action is resistedby the fixed roller 109. Therefore, when a rise on the cam 106 engagesthe roller 105 and tends to move it toward the right, as viewed in FIG-URE 4, it will pivot the lever 136 about the roller 109 and move the pin107 to the left and thereby move the slide 57. Shifting of the fulcrum109 really changes the length of the lever arm 134 with respect to thelever arm 135 which is substantially a constant distance. There fore, bylengthening or shortening the lever arm 134 the lateral movement of theslide 57 may be adjusted for a given rise on the cam. Since the cam 106makes a full revolution, regardless of the diameter of the drill,

if the lateral movement of the grinding wheel is changed, the axialmovement of the grinding wheel should correspondingly be changed.Therefore, the roller 103 shown in FIGURES l and 2 which acts on the cam104 is similarly supported on a fulcrum mechanism.

As shown in FIGURE 1, the roller 103 is mounted on the end of a fulcrumlever 136' which is mounted on a pivot pin 137 carried by the support57, and the lever 136 has a fulcrum surface 138 which bears against afulcrum roller 139. The fulcrum roller 139 is rotatably mounted in avertically movable bracket 140 which is threaded on a screw 141. Thebracket 140 has a wing 141' (FIG. 2) integral therewith in which isformed a groove 142 for receiving a pin 143 carried by the bracket 110.This prevents rotation of the bracket 140 relative to the screw 141. Thescrew 141, as shown in FIGURE 9, has a flange 144 and a spaced threadedcollar 145 threaded thereon by means of which it is supported in a bore146 formed in the member 114, whereby when the extension 114 isvertically adjusted by the screw 116, the screw 141 will also bevertically adjusted in the same proportion. Attention is invited to thefact that the fulcrum adjustment of the lever 136' is for the purpose ofchanging the axial movement of the grinding wheel for the same rise onthe cam, and it is the axial movement of the grinding Wheel thatcontrols the amount of clearance ground on the drill behind the cuttingedges or lips.

It is sometimes desired that this clearance be increased or decreased inspecial cases for the same size of drill, and for the same setting ofthe indicator dial 132. Therefore, it is desirable that the bracket 140be susceptible of vertical adjustment independent of the adjusting screw116. Therefore, the screw 141 is made hollow or tubular and a dependingshaft 147 is fitted in the tubular screw 141 and provided with a keyway148 which is engaged by a set screw 149 mounted in the flanged end 144of the screw 141. This permits the set screw to slide up and down in thekeyway 148 whenever adjustment is effected by the handle 126, but, atany time, the shaft 147 may be rotated to impart rotation to the screw141 and thereby raise or lower the bracket 140 relative to the bracket110. To this end the shaft 147 extends through the fixed housing 117where it is provided with a pinion gear 150 which is in mesh with aninternal gear 151 formed in the rotatable dial 152 mounted on asupporting pivot 153 threaded in the housing 117. Thus, by rotation ofthe dial 152, independent adjustment may be effected by the fulcrumroller 139, and thus the axial movement of the grinding wheel may bechanged relative to its lateral movement.

The mechanism for supporting the work piece and indicated generally bythe reference numeral 65 in FIG- URE 1 is shown more particularly inFIGURES 10 and 11. As shown in FIGURE 1, a knee 154 is supported on thebed of the machine, and this knee is provided with a horizontal dovetailguideway 155 in which is mounted a work slide 156 for movement towardand from the grinding wheel. The slide 156 has a dovetail guideway 157formed therein which, as shown in FIGURE 1, extends at right angles tothe guideway 155. Mounted in the guideway 157, as shown in FIGURE 10,are two slidable members 158 and 159 which have threaded bores 160 and161. The bore 160 is threaded to the opposite hand of the bore 161, andan adjusting screw 162 having opposite threaded portions 163 and 164 isthreaded in the members 158 and 159 wherebyupon rotation of the screw162 the members 158 and 159 will be drawn together or separated,depending upon the direction of rotation of the screw 162.

The screw 162 extends through an angle bracket 165 attached to the slide156 and the screw 162 is provided with a reduced threaded portion 166and upon one side of the bracket is threaded a collar 167, and on theother side an operating knob 168. The members 158 and 159 have workclamping members 169 and 170 secured thereto as by clamping screws 171.The members 169 and 170 have V notches 172 and 173 formed in theopposing faces thereof in which the work piece 29 is mounted and clampedby operation of screw 162 The slide 156 is provided with a rack 174 onits underside which meshes with a gear 175 keyed to a shaft 176 as shownin FIGURE 1. The shaft 176, as shown in FIGURE 2, extends through theside of the knee and is provided with an operating handle 177 wherebyupon actuation of the handle the gear 175 will be rotated to move thework piece toward or from' the grinding wheel. The end of the slide 156carries amicrometer adjusting screw 178 which has a graduated rotator179 splined on the screw which is movable relative to a fixed arrow 180.A spring 179' is interposed between the rotator and the head 180 of thescrew. The adjusting screw is provided with a fine thread which isthreaded in a nut 181 carried by the slide 156, and the end of thisscrew is adapted to engage an abutment 182 formed on the knee 154 to actas a stop and limit the movement of the work toward the grinding wheel.After a predetermined amount of grinding time, the micrometer screw maybe adjusted and the work moved in again, until it hits the stop, by thecontrol lever 177. By this means any number of increments of stock maybe removed from the. end of the drill.

Mechanism is also provided on the knee for rotatably locating the drillto orient it in a proper starting position. This mechanism comprises aswinging arm 183 shown in FIGURE which is rotatably mounted on aneccentric boss 184 of a supporting pin 185. The supporting pin 185 hasreduced ends which are mounted in a bifurcated bracket 186 (see alsoFIG. 2) projecting from the side of the knee 154. The arm has aprojecting lug or stop 187 which is adapted to engage the wall 188 ofthe knee 154- when the arm 183 is swung counterclockwise by a spring189. The arm 183 has a gooseneck extension 191 in the end of which isformed a bore 191 for receiving a work positioning thimble 192. Thethimble has a conical depression 193 formed therein as shown in FIGURE14 for receiving the end of a drill, such as 29. In this depression isformed a suitable radially extending stop 194 which is adapted to engagea lip on the drill.

It will be understood that the member 192 can be oriented in anysuitable position to rotatably position the drill in accordance with theorientation of the cam member on the carrier 53. When this is done, thememher 192 may be clamped in position by suitable set screw means suchas 195 as shown in FIGURE 13. The arm 183 is moved into the positionshown in FIGURE 10 by the operator whenever it is desired to locate anew work piece, and the arm 183 is provided with a stop pin 196 engaginga fixed surface 197 on the knee 154-. This stop member may be adjustedby set screw means indicated by the reference numeral 198. Thus, whenthe arm 183 is rotated clockwise to position the locator 192 its axialcenter may be aligned with the theoretical center 199 of the work asdetermined by the jaws 172 and 173. It will be understood that the arm183 is swung into position and then the slide 156 is advanced by itsoperating lever 177 to insert the end of the drill into theslocater.When this is done, an offset arm 201' (FIG. 11) on a spring pressedlever 211i mounted on the side of the carriage 156 will be inserted in aslot 292 formed in the face of the lever 183. The lever 200 is pivotallymounted on a supporting pin 203 which is threaded in the member 156 andprovided with a spring 204 which urges the lever toward the right asviewed in FIGURE 11. A pin 265 mounted in the slide 156 engages one endof the lever 260 to prevent its rotation about its supporting pin 263.Therefore, as the slide 156 is advanced, the portion 201 will enter theslot 202 and bear against the wall 205' of the. slot 202' and urge thestop pin 196 against the locating surface 197. To limit advance of theslide 156, the lever arm 183 is provided with a stop screw 29 7 which isthreaded therein to project into the slot 2132 and in alignment with themember 201. When the drill has been properly located, the clamping jaws169 and 171 are tightened to clamp the drill in the slide 156 and thenthe slide is retracted so that the lever 183 may be swung out ofposition as shown in FIGURE 2 to permit grinding of the drill.

It is, of course, necessary to true the grinding wheel, but the specifictype of truing mechanism forms no part of the present invention exceptthat it is desirable to select a truing position for the grinding wheeland provide means to stop it in that position. It is contemplated tomount the truing mechanism on the support 57, and therefore it ismovable therewith. As shown in FIGURE 12, the grinding wheelcontinuously moves in a circular path 208 about the axis 64 of therotatable carrier 53. Means are provided for stopping the grinding Wheelin a vertical plane about the center 64 of the carrier 53 with theunderstanding that the truing tool will move in this vertical planewhich will coincide with a diametrical plane of the grinding wheel. Ofcourse, this truing tool will move at an angle in this plane parallel tothe conical surface of the wheel.

To this end of the rotary carrier 53 is provided with a locating notch209 in its periphery .as shown in FIG- URE 12 and the support or slide57 is provided with a stop plunger 210 having a roller 211 mounted inthe end thereof. The plunger is mounted in the support 57 on a radiusfrom the center 64 and a set screw 212 is threaded in the support 57having a projecting end 213 which fits in a slot 214 to prevent rotationof the plunger 210 and to hold the axis of rotation of the roller 211parallel to the axis 64-. A spring 215 is interposed between a washer216' and a non-metallic switch actuator 217 which is backed up by a nut218 threaded on the end of the plunger. The switch actuator 217 engagesa springlike arm 219 which is adapted to actuate a limit switch 220.Normally, the spring 215 holds the plunger 211) in a retracted positionsufiicient for the roller 211 to clear the carrier 53. In axialalignment with the plunger 210 is a control plunger 221 which has a bore222 and a slightly smaller bore 223. A headed rod 224 is slidablymounted in the bore 223, and its enlarged head 225 engages the end of aspring 226- mounted in the bore 222. A threaded plug 227 is threaded inthe end of the bore 222 to hold the spring compressed.

The plunger 221 is slidably mounted in a bushing 228 weided or otherwisesecured to a fixed part of the machine, and the bore 229 of the bushinghas an axially extending slot 231) formed therein. The plunger 221 has astud 231 secured in its periphery .andnormally the plunger 221 isinserted in the bore 229 with the stud 231 in register with the slot230. The plunger is normally held in this position by a spring pressedpin 232 shown in FIGURE 5 which is mounted in bushing 228 and engages anindentation 233 formed in the periphery of the plunger 221. This locatesthe parts so that the end of the member 224 is in engagement with theendof the plunger 210 and the spring 215 is strong enough to overcomethe spring 226 and thereby hold all of the parts in a sufficientlyretracted position that the roller 211 clears the carrier 53 and thelimit switch 220 is open. When it is desired to stop the machine fortruing, the operator pushes on the plunger 221 to complete movement ofthe stud 231 through the bushing and then the operator turns the plunger221 until the stud 231 engages notched recess 234 formed on the insideend of the bushing 228. This compresses the spring 226 sufiiciently tourge the roller 211 into engagement with the periphery. ofv therotatable carrier 53. When the notch 209 comes opposite the roller 211,the plunger 210 is shifted to the left as viewed in FIGURE 12, and theswitch lever 219 is operated to close the limit switch 220.

When the limit switch 220 closes, it completes an 1 1 electricalcircuit, indicated generally by the reference numeral 235 to a solenoid236.

Referring to FIGURES 6 and 7, the solenoid 236 has its plunger 237operatively connected by a bell crank 238 to the upper end 239 of theclutch shifter fork 100 which is pivotally mounted at 240. It will nowbe seen that when the solenoid is energized, the plunger 237 will movedownward as viewed in FIGURE 7 and rotate the shifter fork to disengagethe clutch teeth 95 and thereby disconnect the clutch member 96 from thedriving gear 94 against the resistance of spring 98. It will be realizedthat the clutch member 96 is keyed to the shaft 62 and gear 61 as shownin FIGURE 2 and that this shaft does not rotate at a very high speed.Therefore, as soon as the clutch member is disengaged, the friction ofthe rotating parts driven by the gear 61 will immediately start to slowdown. However, to insure that the clutch member 96 stops almostimmediately, the face 241 is serrated with radial grooves, and aknife-edged plunger 242 is supported in position for engaging thesegrooves when the clutch member 96 is shifted to the right, as viewed inFIG. 6, to immediately stop rotation of the carrier 53 and withsuflicient accuracy to place the grinding wheel in its truing position.

When the operator desires to start the machine again he merely turnsplunger 221 until the stud 231 is aligned with the slot 230 whereby thespring 215 will return the parts to their starting position anddeenergize the solenoid 236.

In the operation of the machine, the motor is started and runscontinuously, operating the parts connected thereto. The general layoutof the cams which control the lateral and axial movements are shown inFIGS. 15 and 16. As shown in FIGURE 15, the lateral control cam 106rotates clockwise, and is spring held against the roller 105. The cam isshown in its midposition with its axis 64 coaxial with the axis 66 ofthe drill shown above the cam. In other words, the radius R is equal tothe radius R of the cam. At the same time, the roller 103 (FIG. 16) isin engagement with the lowest point of the axial control cam surface104. Since the cam 104 is spring held against the roller 103, this meansthat the grinding wheel support is spaced axially its greatest distancefrom the drill.

The cam 106 has a profile such that when it is rotated clockwise a fewdegrees so that the point 243 engages the roller 105, a quickpositioning movement is effected which places the grinding wheel in theposition shown in FIGURE 18. Simultaneously, the rise on cam 104 effectsan axial shifting of the grinding wheel toward the work, so that thegrinding wheel just touches the work. The axis 64 which is thegenerating axis now moves to the left of the drill axis 66 as viewed inFIGURE 15. This corresponds to the shifting movement along the axis 26areferred to in connection with FIGURE 17.

The radius of the cam 106 decreases from the point 243 to about thepoint 244, which means that the axis 64 continues to move to the left,while the rise on cam 104 continues to move the grinding wheel towardthe work, and the grinding wheel continues to move about the axis 64 andreaches the position 20a--20a shown in FIGURE 17. This completes thegrinding cycle for one lip. The cams continue to rotate and effect arepositioning movement and then repeat the generative grinding cycle.

During the second grinding cycle, attention is invited to the fact thatthe section of the cam 106 from point 245 to the point 246 is ofconstantly increasing radius, due to the fact that the axis 64 is nowbeing moved to the right of the drill axis. Therefore, the cam has twosections, one of decreasing radius, and one of increasing radius. Theaxial movement is the same in each case.

There has thus been presented a new and improved method and apparatusfor generative grinding of drills.

What is claimed is:

1. The method of pointing the end of a drill by rotating a grindingwheel about its own axis, said grinding wheel having a grinding facethereon made up of a succession of generative line elements, andrelatively bodily moving the grinding wheel face and the end face of thedrill while in mutual contact in an orbital cycle, one about the other,in a conical spiral path, the drill and grinding wheel being positionedat the beginning of the cycle with a generative line element in thegrinding face of the wheel intersecting the axis of the drill at anacute angle with one finite end of the element extending beyond the axisof the drill a predetermined amount, and continuing said movement in aconical spiral path until and after said finite end passes through saiddrill axis.

2. The method of grinding the cutting face of a fluted drill by means ofa grinding face on a rotatable grinding wheel, said grinding face havingan active generative line element lying in a radial plane containing theaxis of the wheel, said line element terminating in angular relation toa reference axis lying in said radial plane containing said wheel axis,positioning the drill with its axis intersecting the active line elementwith one finite end of the element extending beyond the axis of thedrill a predetermined amount and with the axis of the drill parallel tosaid reference axis with its cutting face in tangential relation to saidgrinding face along a line on the cutting face of the drill passingthrough an intermediate space of a drill flute, gyrating one of saidfaces relative to the other about one of said parallel axes, andsimultaneously effecting relative bodily movement between said faces indirections axially and laterally with respect to said axis of gyrationto cause the said one finite end of the active line element to movethrough the drill axis and a predetermined amount therebeyond while thecutting face of the drill moves toward the grinding face of the wheel.

3. The method of grinding the cutting face of a fluted drill by means ofa grinding face on a rotatable grinding wheel, said grinding face havingan active generative line element lying in a radial plane containing theaxis of the wheel, said line element terminating in angular relation toa reference axis lying in said plane, positioning the drill with itsaxis intersecting the active line element with one finite end of theelement extending beyond the axis of the drill a predetermined amountand with the axis of the drill parallel to said reference axis with itscutting face in tangential relation to said grinding face along a linepassing through an intermediate space of a drill flute, gyrating one ofsaid faces relative to the other about one of said parallel axes, andsimultaneonsly moving said axis of gyration and thereby one of saidfaces axially and laterally relative to the other to effect twodirectional movement therebetween to cause the said one finite end ofthe active line element to move through the drill axis and apredetermined amount therebeyond while the cutting face of the drillmoves toward the grinding face of the wheel.

4. In a drill grinding machine having a base and a drill holding fixturethereon, the combination of means for supporting a grinding wheel on thebase for relative movement with respect to the fixture comprising agrinding wheel spindle, a rotatable carrier supporting said spindletherein parallel to but eccentric of the axis of rotation of thecarrier, a sub-support mechanism for support ing the carrier on the basefor bodily movement in nor mally related directions, and means to impartrotation and said bodily movements to the carrier simultaneously.

5. In a drill grinding machine having a base and a drill holding fixturethereon, the combination of means for supporting a grinding wheel on thebase for relative movement with respect to the fixture including agrinding wheel spindle, a rotatable carrier supporting said spindletherein parallel to but eccentric to the axis of rotation of thecarrier, means to impart rotation to the spindle, means to impartrotation to the carrier, and means to impart bodily movement to thecarrier in two normally related directions simultaneously duringrotation of the spindle and carrier.

6. In a drill grinding machine having a bed, means to support a drillwith its axis parallel to the plane of the bed, a sub-support guided onthe bed for two directional movement parallel to the plane of the bed, arotatable carrier journaled on the sub-support for rotation about anaxis parallel to the plane of the bed and to the drill axis, a grindingwheel spindle journaled eccentrically in the carrier with its axisparallel to the axis of the carrier, and power operable means forrotating said carrier and simultaneously imparting two directionalmovement to said subsupport in prescribed synchronized relation.

7. In a drill grinding machine having a bed, means thereon to locate andclamp a drill in grinding position, a rotatable carrier supporting agrinding wheel, means mounting the carrier on the bed with its axis ofrotation co-axial with the axis of the drill, means to laterallyoscillate the carrier equal distances to either side of said drill axis,and means to impart movement to the carrier parallel to its axissimultaneously in one direction as the carrier axis moves away from thedrill axis, and in an opposite direction as the carrier axis movestoward the drill axis.

8. In a drill grinding machine having a base, and means thereon forlocating and clamping a drill to be ground, the combination of agrinding wheel spindle, a rotatable carrier supporting said spindleeccentric to its axis, a sub-support for supporting said carrier on thebase with its axis coaxial of the drill axis, means to impart movementto the carrier parallel to and normal to its axis including control camsattached to said carrier, a follower roller for each cam, a lever armsupporting each roller and pivotally connected to the sub-support, and afulcrum roller carried by the bed in engagement with said levers.

9. In a drill grinding machine having a base, and means thereon forlocating and clamping a drill to be ground, the combination of agrinding wheel spindle, a rotatable carrier supporting said spindleeccentric to its axis, a sub support for supporting said carrier on thebase with its axis coaxial of the drill axis, means to impart movementto the carrier parallel to and normal to its axis including control camsattached to said carrier, a follower roller for each cam, a lever armsupporting each roller and pivot ally connected to the sub-support, afulcrum roller carried by the bed in engagement with said levers, andmeans to shift said fulcrum rollers parallel to said levers.

10. In a drill grinding machine having a base, and means thereon forlocating and clamping a drill to be ground, the combination of agrinding wheel spindle, a rotatable carrier supporting said spindleeccentric to its axis, a sub-support for supporting said carrier on thebase with its axis coaxial of the drill axis, means to impart movementto the carrier parallel to and normal to its axis including control camsattached to said carrier, a follower roller for each cam, a lever armsupporting each roller and pivotally connected to the sub-support, and afulcrum roller engaging each of said lever arms and carried by the bed,and means to independently shift said fulcrum rollers parallel to theirrespective lever arms.

ll. In a drill grinding machine having a base, and means thereon forlocating and clamping a drill to be ground, the combination of agrinding wheel spindle, a rotatable carrier supporting said spindleeccentric to its axis, a sub-support for supporting said carrier on thebase with its axis coaxial of the drill axis, means to impart movementto the carrier parallel to and normal to its axis including control camsattached to said carrier, a follower roller for each cam, a lever armsupporting each roller and pivotally connected to the sub-support, and afulcrum roller engaging each of said lever arms and carried by the bed,means to simultaneously shift said fulcrum rollers parallel to theirrespective lever arms, and additional means to shift one of said rollersindependently of the other.

12. In a drill grinding machine having a bed, means thereon to supportand clamp a drill to be ground, a

grinding wheel spindle, a rotatable carrier for supporting position fortruing the grinding wheel includinga spring pressed plunger, saidcarrier having a locating notch thereon in predetermined relationcircumferentially with respect to the axis of the spindle, means torelease said plunger for engagement with said notch, and electricalmeans automatically operable upon engagement of the plunger with saidnotch to stop rotation of the carrier.

13. The method of grinding the cutting face of a fluted drill byrotating a grinding wheel about its axis, said grinding wheel having agrinding face thereon made up of a succession of generative lineelements extending crosswise of said face and terminating in a radiusformed by a rounded corner on the wheel, positioning a portion of thecutting face to be ground in opposition to and in grinding relation withsaid grinding face and with the axis of the drill intersecting thegrinding face at a predetermined angle, eifecting rotation of thegrinding wheel, and while the wheel is so rotating, effecting a gyratorymovement between said opposed faces while maintaining said angleconstant to effect a grinding operation and to generate a surface inaccordance with the shape of said line elements, and simultaneouslyeffecting an additional relative movement between said faces both in thedirec tion of the axis of the drill and also normal thereto to causesaid radius to move through and beyond the axis of the drill andthereby'eifect the shaping of a point on the axial end of the drill, andcontrolling said gyratory, movement in timed relation with saidadditional movement to cause grinding of a spiroidal surface on thecutting face simultaneously with the shaping of said point.

14. The method of generating a cutting face on the end of a fluted drillhaving a cutting edge extending cr0ss-. wise of its axis between thebottom of said flutes and connected at its ends to the lips of the drillwith onehalf of each side face of the cutting edge forminga cutting faceand the other half a flank face, said method comprising rotating agrinding wheel havinga grinding face about its own axis, said grindingface being made up of asuccession of generative line elements extendingcrosswise of said face and terminating at one end in a radius formed bya rounded corner on the wheel, and relatively moving the grinding faceof the wheel and the cutting face of the drill while in mutual contactin a conical spiral path, the grinding face of the wheel and the cuttingface of the drill being positioned at the beginning of the cycle with aline element in the grinding face intersecting the axis of the drillwith the radius end of the element extending beyond the axis of thedrill a pr determined amount, and continuing the relative spiralmovement of the grinding Wheel and drill until and after the radius endof the element passes through and beyond the drill axis whereby therounded corner will grind a spiroidal surface on the flank face and thecutting face on one side of said cutting edge While said grinding facegrinds a conical spiral surface on the end of said drill.

15. The method of generating a cutting face on the end of a two-flutedrill having a cutting edge extending crosswise of its axis between thebottom of said flutes and connected at its ends to the lips of the drillwith one-half of each side face of the cutting edge forming a cuttingface and the other half a flank face, said method comprising rotating agrinding wheel having a grinding face about its own axis, said grindingface being made up of a succession of generative line elements extendingcrosswise of said face and terminating at one end in a corner on thewheel, and relatively moving the grinding face of the wheel and thecutting face of the drill while in mutual contact along a conical spiralpath while rotating the drill relative to the wheel through an angle ofmore than 90 degrees and less than 180 degrees, the grinding face of thewheel and the cutting face of the drill being positioned at thebeginning of the cycle with a line element in the grinding faceintersecting the axis of the drill with the one end of the elementextending beyond the axis of the drill a predetermined amount, andcontinuing the relative spiral movement of the grinding wheel and drilluntil and after the one end of the element passes through and beyond thedrill axis whereby said one end first will grind a spiroidal surface onth flank face and the cutting face on one side of said cutting edgewhile the grinding face grinds a conical spiral surface on the cuttingface of the drill.

16. The method recited in claim wherein said one end of the generativeline element is terminated in a radius formed by a rounded corner on thewheel.

17. The method recited in claim 16 wherein the angle made by the axis ofthe drill with the face of the grinding wheel is maintained constantduring relative movement of the grinding face and the drill along saidconical spiral path.

18. The method recited in claim 16 wherein the grinding wheel and drillare positioned with their axes parallel to one another, and wherein saidaxes are maintained in such relationship during said relative movementof the grinding face and the drill.

19. In a drill grinding machine, the combination of a bed, a carriermounted on said bed for rotary, axial and lateral movements eitherindividually or in combination, a grinding wheel spindle journaled onsaid carrier with its axis parallel to but displaced from the axis ofsaid carrier, means to rotate said carrier, and means operating insynchronism with the rotation of said carrier for imparting timed axialand lateral movements thereto whereby said grinding wheel spindle willbe given corresponding axial and lateral movements as it is gyratedabout the axis of said carrier.

20. In a drill grinding machine, the combination of a bed, a supportmounted on said bed for movement in two mutually perpendiculardirections, a carrier journaled in said support for rotation about anaxis parallel to one of said directions of movement, a grinding wheelspindle journaled on said carrier with its axis parallel to butdisplaced from the axis of said carrier, means to rotate said carrier,and means operating in synchronism with the rotation of said carrier tomove said support in said two directions whereby said grinding wheelspindle will be given coordinated axial and lateral movements as it isgyrated about the axis of said carrier.

21. In a drill grinding machine for generating a cutting face on the endof a drill having longitudinally extending flutes and a cutting edgeextending crosswise of its axis between the bottom of said flutes withone half of each side face of the cutting edge forming a cutting faceand the other half a flank face, the combination of a grinding wheelhaving a grinding face thereon made up of a succession of generativeline elements extending crosswise of said grinding face and terminatingat one end in a radius formed by a rounded external corner on the wheel,means for holding the drill with its cutting face in tangential relationto the grinding face and with the axis of the drill intersecting one ofsaid generative line elements, cyclically operable means for effectingrelative rotation between the grinding face of the wheel and the cuttingface of the drill, and means including a pair of cams operated by saidcyclically operable means for imparting timed lateral and axialmovements of the grinding face relative to the cutting face to cause therounded corner to move across the axis of the drill and in so doing togrind the flank face and the cutting face on one side of the cuttingedge While the grinding face simultaneously grinds a conical spiralsurface on the cutting face of the drill.

22. The drill grinding machine of claim 21 wherein said movementimparting means includes a cam follower for each of said cams, andmanually adjustable means cooperating with said cam followers forvarying the effective throw of said cams whereby the machine may beadjusted to grind different size drills.

References Cited in the file of this patent UNITED STATES PATENTS546,041 Tyberg Sept. 10, 1895 641,107 Heister Jan. 9, 1900 1,652,672Jackson Dec. 13, 1927 1,759,196 Jackson May 20, 1930 2,328,549 Eich etal. Sept. 7, 1943 2,471,539 Parker May 31, 1949 2,529,026 Kestell Nov.7, 1950 2,538,651 Parker Jan. 16, 1951 2,869,403 Bemt Jan. 20, 19592,903,922 Ernst et al Sept. 15, 1959 FOREIGN PATENTS 250,713 SwitzerlandJuly 1, 1948 1,006,695 France Jan. 30, 1952

